Gas turbine engines for aircraft, marine, and land use typically have axial flow turbines that comprise a number of rotatable discs, each of which carries an annular array of radially extending airfoils of the blades on its periphery. Each blade airfoil is provided with a root portion by means of which it is attached to its associated disc. While such a method of attachment is effective in ensuring the integrity of each blade/disc assembly, problems can still arise because of airfoil vibration. Such vibration, if unchecked, may lead to reduction in blade life, and in some cases rapid damage to the blades.
The airfoils are generally designed to have high tolerances to accommodate significant operational requirements such as crosswinds. However, the airfoils may be prone to high vibratory responses and possible aero elastic instability within some operational speed ranges that may result in flutter. Airfoil flutter is a result of complex interactions between fluid flow, stiffness, and inertial forces on an airfoil.
To resist flutter, the airfoils are designed to have sufficient torsional stiffness, bending stiffness, and structural damping. However, some structural damping may also result in an addition of weight to the airfoil. Therefore, it is desirable to have a damper to the airfoil that would effectively address torsional vibration without increasing the airfoil weight.